1. Field of the Invention
The present invention relates to power generation apparatuses that extract power generated by a thermal engine to the exterior of the thermal engine.
2. Description of the Related Art
Among thermal engines, external combustion engines are configured to convert heat into power (convert heat energy into kinetic energy) by expanding and condensing a working medium (also referred to as a working fluid), such as water or a low-boiling point medium (a medium having a lower boiling point than water) such as ammonia, pentane, Freon, or the like, through a thermodynamic cycle such as a Rankine cycle. Such a thermal engine includes an expander that expands working medium vapor, and the expander is contained within a housing that is separated from the exterior in an airtight state. Rotational driving force obtained through this expander is extracted to the exterior of the housing in which the expander is contained via a shaft, and is used to rotate a rotating machine such as a compressor, a blower, a pump, an electric generator, or the like.
For example, JP-2009-185772A discloses a fluid machine, including an expanding mechanism that generates rotational force by expanding a working fluid, an electric generator driven by the rotational force of the expanding mechanism, and a pump mechanism driven by the rotational force of the expanding mechanism, in which the fluid machine is configured so that the volume of the pump mechanism is variable.
Meanwhile, U.S. Pat. No. 7,249,459 discloses a fluid machine including an expander that converts heat energy from a Rankine cycle into rotational power, a liquid supply pump that is driven by the rotational power and increases the pressure in the Rankine cycle, and a motor that generates rotational driving force, in which a rotating shaft is shared by these elements.
These apparatuses (fluid machines) both contain an expander, which is part of a thermal engine, and a rotating machine such as an electric generator or a pump together within a single housing.
Incidentally, with the apparatuses (fluid machines) disclosed in the aforementioned background art, it is absolutely necessary to provide a seal in the housing that contains the expander in order to prevent the working medium from leaking.
In the case where an expander and a rotating machine such as an electric generator or a pump are contained within a single housing, as disclosed in JP-2009-185772A, there are situations where a shaft seal for a shaft that connects the expander and the rotating machine is not needed. However, specialized components are required for the housing or the rotating machine, which poses a problem in that generic components cannot be used. This can also easily lead to an increase in the initial costs of the power generation apparatus or electricity generation equipment that uses the power generation apparatus.
On the other hand, in the case where a rotational shaft for transmitting power passes through the housing and protrudes to the exterior, as shown in U.S. Pat. No. 7,249,459, a seal for the shaft is important particularly in binary electric generation, in which a low-boiling point medium, which should not be exposed to the atmosphere, is used as the working medium. With the equipment shown in U.S. Pat. No. 7,249,459, a structure is employed in which a shaft seal is provided between a rotary machine (a motor 9) and an expander, and thus the working medium does not leak toward the rotary machine. However, it is difficult to prevent the working medium from leaking with certainty even if this type of shaft seal is employed, and it is also necessary to carry out complicated maintenance procedures on the shaft seal. Further, this can easily lead to an increase in the running costs of the power generation apparatus or electricity generation equipment that uses the power generation apparatus.
Having been achieved in light of the stated problems, it is an object of the present invention to provide a power generation apparatus capable of efficiently transmitting rotational driving force generated by an expander to the exterior of a housing that contains the expander while preventing a working medium from leaking, even when the thermal engine and a rotary machine are not contained together within a single housing, or when a shaft sealing mechanism is not employed on a shaft that transmits power.